This invention pertains to novel photographic elements and to methods of processing such elements. More specifically, the invention relates to color photographic elements which have faithful rendition or reproduction of the red color.
Achieving faithful color rendition is the goal for many color products. One of the factors that influences the ability to faithfully render color in a color negative system is the spectral sensitivity distribution of the silver halide emulsions used in the photographic element. Most color negative photographic elements include at least one blue-sensitive silver halide emulsion layer containing a yellow image dye-forming compound, a yellow filter layer, at least one green sensitive silver halide emulsion layer containing a magenta image dye-forming compound, and at least one red-sensitive layer containing a cyan image dye-forming compound. The structure below represents such a conventional photographic film.
______________________________________ Structure 1 ______________________________________ OVERCOAT FAST YELLOW SLOW YELLOW YELLOW FILTER LAYER FAST MAGENTA SLOW MAGENTA FAST CYAN SLOW CYAN ANTI HALATION LAYER SUPPORT ______________________________________
It is known in the art that the spectral sensitivities of these layers overlap, with the largest overlap being the green (and short red) sensitivity of the red-sensitive records. The present inventor has found that faithful color rendition cannot be achieved with this unwanted green light sensitivity of the red-sensitive layers because green light will expose the red-sensitive layers and thus lead to cyan image dye formation when the film is developed. FIG. 1 illustrates the spectral sensitivity of a red-sensitive color record present in a color negative photographic element having a structure as described in Structure 1. The peak sensitivity of this color record occurs at 655 nm. However, it is clear that the red-sensitive record also has sharply increasing green light (and short red) sensitivity from 550 nm to 620 nm as indicated by the cross hatched region in this Figure.
In many color photographic materials, in particular color negative materials, it is now common practice to incorporate in at least one layer of the photographic element, a compound which reacts with the oxidation products of a color developer to release a development inhibiting compound. This development inhibiting compound may inhibit development in the layer in which it was released, that is, have an intralayer effect, or it may diffuse into an adjacent layer and inhibit development, that is, have an interlayer effect.
These development inhibitor releasing compounds known as DIR's in the photographic art, have been proposed to be used in various layers and in various ways in color photographic materials to give both intra- and inter-layer effects. The use of the interlayer restraining effect has been known as a useful means for improving color reproduction of color photographic materials. In color negative photographic materials, for instance, the development restraining effect from the green-sensitive to red-sensitive layers may restrain color formation in the red-sensitive layers and thus help correct the unwanted green sensitivity of the red-sensitive layers when the photographic element is exposed to white light. However, when the exposure is in the 580 to 620 nm range, no corresponding sensitivity of the green-sensitive element is present and therefore there is not suppression of the cyan dye formation by the green-sensitive record. Thus faithful color rendition cannot be achieved by this interimage effect.
U.S. Pat. No. 4,705,744 is directed to a method of improving color reproduction of a photographic material by including an image dye-forming donor layer in the multilayer film. The donor layer contains, in addition to the image dye-forming compound, a silver halide emulsion which is chemically finished and spectrally dyed having a wavelength weighted-average spectral sensitivity at least 5 nm shorter than the wavelength weighted-average spectral sensitivity of the green-sensitive layers, that is, less than 545 nm for the green spectral sensitivity distribution shown in FIG. 1. The donor layer also contains a DIR compound that can act upon the red-sensitive layers.
U.S. Pat. No. 4,306,015 discloses a method of improving color reproduction by including a nonimage dye-forming donor layer in the multilayer. This donor layer also contains a chemically finished and spectrally dyed silver halide emulsion and a DIR compound that leads to low, that is less than ten percent, or no dye formation when the DIR compound reacts with the oxidation products of a color developer. The released inhibitor provides the desired interlayer effects. Recommended peak spectral sensitivities for the donor layer are 670 nm or 520 nm.
However, these donor layers of the prior art do not provide a photographic element having a faithful rendition of red color. The present inventor has found that this is because these donor layers are insufficient in reducing the unwanted green (and short red) sensitivity of the red-sensitive layers of a color sensitivity of the red-sensitive layers of a color photographic element in the spectral region from 550 nm to 620 nm.
Accordingly, there is a need to provide a photographic element having faithful red color rendition. Additionally, there is a need to make efficient use of all light that enters into the photographic element at the time of exposure and, whenever possible, exploit the beneficial interimage effects of the developer inhibitor releasing compounds. Finally, there is a need to control the timing of the release of the development inhibitor releasing compound in order to get faithful rendition of a red color.